3.54GHz 10W envelope tracking amplifier with 43% efficiency utilizing the 1.5 bit-high efficiency envelope amplifier

This paper presents a 1.5 bit (3-level) envelope amplifier to improve the overall efficiency of wideband high linearity envelope tracking power amplifier. The proposed envelope amplifier has been devised with two switches providing the different supply voltages. Since the unnecessary current (ripple current) induced by a switching stage can be reduced by the multi-level quantization, the efficiency of a proposed envelope amplifier is 5% higher compared with that of a conventional architecture. With the proposed envelope amplifier, we have designed and implemented the 3.54 GHz high efficiency envelope tracking power amplifier using a commercial 60 W PEP GaN device. The efficiency boosting effect is further verified by the measured results. The experiment results show that the envelope tracking power amplifier operates at drain efficiency (DE) of 43.6% and power added efficiency (PAE) of 39.2% and a gain of 10.1 dB at average output power of 40 dBm for a 10 MHz WiMAX signal with 8.5 dB peak-to-average power ratio (PAPR). By using digital predistortion function, the adjacent channel leakage ratio (ACLR) is less than -45.4 dBc at 20 MHz offset.